Untangling the landscape of deer overabundance: Reserve size versus landscape context in the agricultural Midwest

We investigated the potential for cross-habitat interactions to modulate per capita ungulate browse effects on forest herbaceous layers. Specifically, we examined how white-tailed deer (Odocoileus virginianus) abundance, reserve size, and landscape context at variable spatial scales interact to influence the impact of deer herbivory on forest understory communities in 16 Indiana state parks. We used native herb cover (NHC) as a proxy for deer impact to forest understories, and deer killed per unit hunter effort (DAI) as a proxy for deer abundance. Comparison of multiple regression models, using Akaike’s Information Criterion, suggested that the per capita impact of deer herbivory to forest understories was strongly related to landscape configuration of deer habitat types at the scale of an individual deer’s home range, whereas deer abundance was more strongly associated with landscape structure at broader spatial scales. Interspersion and juxtaposition of non-forested, perennial forage habitat with other habitat types (forest and agriculture) at the park plus a 0.5 km buffer scale, together with DAI, explained 84% of the variation in native herbaceous cover (NHC). A model with DAI alone as a predictor accounted for only 19% of the variation in NHC. Thus, although deer impact was related to deer abundance, habitat configuration in landscapes surrounding parks appeared to strongly modulate the level of impact associated with a particular abundance of deer. Our results underscore the importance of landscape context in determining foraging behavior and per capita impacts of ungulates on forest resources in protected areas.